Blank for siftproof cartons



July 30, 1968 s. M. SILVER 3,394,866

BLANK FOR SIFTPROOF CARTONS Filed Jan. 4, 1.967 4 Sheets-Sheet 1 I N VENTOR.

STANLEY MILTON SILVER BY ATTORNEY July 30, 968 s. M. SILVER 66 BLANK FOR SIFTPROOF CARTONS Filed Jan. 4, 1967 4 Sheets-Sheet 2 FIG.4 F|G.3

INVENTOR.

STAN LEY MILTON SILVER BY ATTORNEY July 30, 1968 s. M. SILVER BLANK FOR SIFTPROOF CARTONS 4 Sheets-Sheet 3 Filed Jan. 4, 1967 m WV TL I WM m ATTO R N EY July 30, 1968 s. M. SILVER BLANK FOR SIFTPROOF CARTONS Filed Jan. 4. 1967 4 Sheets-Sheet. 4

FIG

FIG."

INVENTOR. STANLEY MILTON SILVER ATTOBRE! United States Patent 3,394,866 BLANK FOR SIFTPROOF CARTONS Stanley Milton Silver, 10 Blenheim St., London W. 1, England Filed Jan. 4, 1967, Ser. No. 611,211 Claims priority, application Great Britain, Mar. 3, 1966, 9,315/66; July 18, 1966, 32,186/66 16 Claims. (Cl. 229-37) ABSTRACT OF THE DISCLOSURE The blank for a tubular end sealed carton is provided with inner dust flaps widened by small outwardly-projecting, softened, tooth-like formations on its parallel edges; the projections being formed by providing a tear line between dust flaps and adjacent blank portions formed by closely spaced rows of closely spaced intermittent cuts; the projections being softened by debossing the space between rows of cuts; the cuts of the two rows being staggered relative one another.

The present invention relates to side-seamed, endsealed, rectangular, tubular cartons and, especially, to siftproof cartons of the character described and, more specifically, to the blanks fi'om which such siftproof cartons may be formed.

It is the principal object of the present invention to provide carton blanks which, when end-sealed by the method described in my companion application, Ser. No. 607,216, filed Jan. 4, 1967, will automatically produce a carton having an improved, stronger, tighter and more complete seal than possible with conventional carton blanks heretofore in use.

More specifically, the object of the present invention is to provide a carton blank which, when passed through standard end-sealing equipment, particularly of the continuous motion, linear movement type, modified in the manner described in my said companion application, will apply, automatically, positive interior pressure of the dust flaps of the carton against the overlying outer closure flap as well as against the walls adjacent to the side edges of the dust flaps, to thereby attain, when exterior pressure is applied in the sealing process, positive and more complete bonding between the dust flaps and the overlying outer closure flap, and to close wholly and completely any space between the edges of the dust flap and the adjacent side walls, to provide a completely siftproof and substantially hermetic seam between them.

It is another object of the present invention to provide carton blanks of the character described whose advantages may be attained without any increase in the cost of the blank, nor in the speed and cost of the sealing operation, over the standard carton blank as heretofore used.

In the drawings:

FIG. 1 is a top plan view, broken across, of one embodiment of a blank of the present invention;

FIG. 2 is an isometric view of a folded, glued and set up blank with the end-forming flaps severed from one another and in position ready for folding and sealing;

FIG. 3 is a more or less diagrammatic view of a constant, linear motion end-sealing apparatus with cartons in various stages of the sealing process;

FIG. 4 is a more or less schematic section taken on line 44 of FIG. 3;

FIG. 5 is a section similar to that of FIG. 4 but taken on line 55 of FIG. 3;

FIG. 6 is a fragmentary, perspective view of the sealed carton end of FIG. 5; shown partly broken away, to disclose details;

3,394,866 Patented July 30, 1968 "ice FIG. 7 is a plan view of the cutting end of a knife for forming the blank of the present invention, partly broken away to illustrate details;

FIG. 8 is a fragmentary, sectional view taken on line 88 of FIG. 7;

FIG. 9 is a section taken on line 99 of FIG. 7;

FIG. 10 is an elevational and partly sectional view showing the knife of FIG. 7 in position for forming the tear line in a carton blank;

FIG. 11 is a view similar to that of FIG. 10, showing the knife in position of cutting and debossing the carton blank; and

FIG. 12 is a fragmentary, more or less diagrammatic view of a portion of the carton blank with the tear line between dust flap and end-closure flap illustrated with a portion of the dust flap broken away, the arrow indicating the course of the grain in the cardboard.

Generally stated, the present invention consists in the adding to the width of the dust flaps on each side thereof by cutting the additions away from the adjacent closure flaps and/or glue flap and simultaneously conditioning such marginal additions to become relatively softer and bendable and imparting to them gasket-like characteristics; and so cutting and scoring such blanks that they may, when and as the carton is set up and closed for sealing, first, serve to bow the dust flaps along the partly cut fold line provided in them, upwardly, so that the dust flaps will exert, initially, positive pressure against the overlying closure flap, in preparation for the application of exterior sealing pressure, and upon full application of such pressure, their side edges will be compressed against the sides of the carton to form a perfect and imperforate seal. In the preferred embodiment the excess width of the dust flapis provided in the form of a serrated edge; still more preferably, to have serrations in the form of rectangular indentations or recesses that provide substantially square teeth which are capable of being offset and of spreading under pressure, and between which adhesive may accumulate to be pressed out against the side walls of the cartons and the overlying closure flap to form a most effective, bonded seal, for even micro-pulverized materials.

The invention also resides in the provision of a die knife section which is not only capable of forming the close, relatively tiny serrations or teeth in the edges of the dust flaps, but is also capable of conditioning the teeth at the same time for at least partial defibrillation and to render them relatively soft, bendable, and compressible.

The carton blank of the present invention, as illustrated in the drawings, is shown to be of generally conventional construction, being cut and scored to provide front and rear wall panels, 10 and 12, each one formed with an outer closure flap, 14 and 16 respectively, at its ends, defined from wall panels 10 and 12 by fold lines, 15 and 17; the end wall panels, 18 and 20, each formed with an inner dust flap, 22 and 24 respectively, at their ends, defined from the end wall panels by fold lines, 23 and 25; and a glue flap, 26, along one longitudinal edge of the blank. The closure flaps 18 and 20 may each be of a height greater than half the width of an end wall panel and, preferably, equal to such width. The dust flaps 22 and 24 are of a height not exceeding half the width of the front and rear panels 10 and 12.

The blank of the present invention departs from the conventional in the formation of the dust flaps 22 and 24 which are of greater width than the end wall panels 18 and 20 from which they extend; the excess width being provided by lateral extensions on each side of the panel taken from the width of the adjacent marginal edge portions of flaps 14 and 16 and from the material of the glue flap 26, when the glue panel extends from the edge of an end wall panel.

Preferably, the edges of the dust flap extensions may be serrated, preferably with serrations in the form of rectangular teeth, 28. Such teeth 28 may be produced by substituting for the conventional cut line at the edges of the dust flaps a tear line formed of a pair of closely spaced rows of short, closely spaced cuts; with the cuts in one row arranged in staggered relation to the cuts in the other. One row of cuts is disposed at the position of the edge of the flap of a normal blank and the other row defining the edge of the extension. With such a tear line, the tooth formation results from the separation of the flaps along it; the material between the cuts being first weakened by stretching during the die-cutting operation. This insures that tearing takes place back and forth between the cuts in the two rows and also defibrillates the side edges of the resulting teeth, to a degree. Preferably, the distance between rows of cuts, the length of each cut and the spaces between cuts may be about the same; namely, about one thirty-second of an inch The blank of the present invention further departs from the conventional in having the fold lines 23 and 25 peaked slightly from their ends towards their center, and in having the fold lines, 30 and 32, formed in the dust flaps 22 and 24 extending longitudinally thereof from the peaks of the fold lines 23 and 25. Preferably, for reasons which will hereafter become clear, the fold lines 30 and 32 may be partly cut through the thickness of the board on its exterior.

The blank of the present invention may be folded and glued in the conventional manner and may be erected in tubular form (FIG. 2) in the conventional way and may be sealed by moving along through the different stages of a conventional constant motion, straight line movement, sealing apparatus, as is diagrammatically illustrated in FIG. 3 of the drawings, with the front and rear walls and 12 disposed parallel to the direction of movement in the apparatus, facing the guide rails, 33, such apparatus being modified by the additions hereafter described.

As conventional, the erected carton in its initial position in the apparatus, shown at A, has the flaps 14 and 16 laterally outwardly offset to horizontal position, while flaps 22 and 24 remain erect. The carton is then moved to position B, where dust flaps 22 and 24 are folded to horizontal position to overlie the carton opening, also as conventional. The carton is then moved to position C, in the course of which movement an adhesive, 31, is applied to selected flaps for adhering one of the closure flaps, as 14, to dust flaps 22 and 24 and the other closure flap to closure flap 14. Such adhesive may be in the form of a glue or a thermoplastic material. It may be applied to the upwardly facing surfaces of the outwardly offset closure flaps 14 and 16, as illustrated, or to the upwardly facing surfaces of the inwardly offset dust flaps 22 and 24, both practices being conventional. When desired, a thickened band, 32, of adhesive may be applied to the marginal portions of the edges of the coated flaps which are adjacent to the front and rear panels 10 and 12; such additional band of adhesive being especially desirable when the carton is to be made siftproof even to micropulverized material.

It will be understood that when a thermoplastic adhesive is used it is applied to the blank before folding and gluing and it is merely reconstituted to adhesive state at position C by the application of the conventional heated knives.

Thereafter, the carton is moved towards position D, in the course of which movement the flap 14, which is the one illustrated as being glue-coated, is plowed into horizontal position to overlie the horizontally offset inner dust flaps 22 and 24, and the adhesive-coated closure flap 16 is then plowed to overlie dust flap 14.

It will be clear that, as dust flaps 22 and 24 are wider than the opening between walls 10 and 12, the plowing of flaps 14 and 16 to overlie them will compress the dust flaps and cause them to become peaked longitudinally along the center, cut fold lines 30 and 32. It will also be clear that such peaking will be in an upward direction against the overlying closure flap 14; such direction being insured by the fact that the cut of the fold lines 30 and 32 is formed in the outer surface of the flaps 22 and 24 and also by the provision of the peaked fold lines 23 and 25 at their base.

From this position, instead of having the flaps pressed against one another from the top to form the end seal, as is conventional, the invention provides for the gradual and progressive compression or pinching of the front and rear walls 10 and 12 slightly toward one another, from one edge of the walls to the other, at a point immediately adjacent the fold lines 15 and 17, to press said walls against the edges of the flaps 22 and 24 and, substantially immediately after commencing the compression or pinching of the walls 10 and 12, to apply pressure from above to the overlying flaps to flatten them out and press the marginal edge portions of flaps 22 and 24 against the carton sides 10 and 12; the combined pressures tending to bend and offset the teeth 28 to provide a greater area of contact between the edges of flaps 22 and 24 with walls 10 and 12. Such pressures also tend to spread out the edges of teeth 28. The combined pressures on the flaps 22 and 24 also tend to press out the glue into the spaces between teeth 28 and into any space between the edges of the dust flaps and side walls of the carton contacted by them, to seal off any such spaces and render the seal siftproof. Where the thickened band of adhesive is applied, an excess amount of glue is pressed out to close such spaces, to make the seal siftproof even for micropulverized material.

The exterior flap-flattening pressure may be applied in any desired manner, as by pressure plate, 36, which is diagrammatically shown in broken lines in FIG. 3 for clarity of illustration.

The pinching pressure may be effected by means of shims forming pinching rails, 38, applied to the inner surface of guide rails 33; such pinching rails 38 being formed with lead edges that are tapered in the direction of their supporting guide rails, to thereby gradually pinch the wall panels 10 and 12 towards one another as the carton is moved between them and thus effect a compression without risk of damage to the carton walls.

It may here be stated that the pinching and sealing pressures may both be continued until the bond between the flaps is set. It may here also be stated that the facing surfaces of the pinch rails 38 may be coated with a permanent plastic lubricant of the type that is frequently used on the guide rails 33 themselves, to reduce the friction on the carton moving between them.

The formation of the blank described above, with the dust flap tear lines described, has been made possible by my development of the cutting-knife die section that may form the double row of intermittent cuts in a cardboard, in such closely spaced relation as was heretofore not commercially possible. Such cutting knife section is shown to consist of a pair of blades each having intermittent, rectangular cut-outs in its cutting edges; the blades being spaced from one another to provide the requisite distance of about one thirty-second of an inch (%2") between them, and the cutting portions of the knives and the spaces between them being formed of a like length, and of shoulder blades arranged to each side of the two blades, the upper edges of the shoulder blades tapering in the direction of the cutting blades and terminating short of such cutting edges. Heretofore, when parallel double cuts were made by parallel cutting blades, the blades Were required to be kept apart a distance sufficiently large to insert between them a strip of resilient material for the purpose of repelling the cut carton and at the same time preventing any particles from the cut materials remaining between the blades and in time clogging the space between them to render them useless.

To make possible the insertion of such resilient material between the cutting blades, the blades had to be kept apart a minimum distance much greater than the ,2-inch required by the production of the carton blank of the present invention. In order, therefore, to provide the resilient repellant between the closely spaced blades of my cutting knife, I have conceived of and do use, instead of a spacing strip of rubber, a material which is sufiiciently fluid to be poured or troweled into the space between the teeth of the blades and above the shoulders to each side of the knife blade, to the level of the edges of the blades, and which material has the characteristic of setting, when left exposed to the air for a short time, into a solid, tough and resilient mass that adheres to the blades and is fully able to perform the function that is performed by the rubber strip in conventional, widely spaced, double-blade cutting knives. The presence of the shoulder blades and of the overlying resilient material makes it possible for the knife, in addition to producing the intermittent cuts, to also produce a debossment which provides the fold line at the base of the teeth as described above, in a manner that will later be more fully described.

It may here be stated that when pouring or troweling the semi-fluid material, the knife may be placed between two flat plates to prevent the fluid from running out before it completely sets and to make the sides of the set resilient body continuous with the outer surfaces of the shoulder blades.

In the preferred embodiment of the double-blade, intermittent cutting knife illustrated in the drawings, two blades, 50, each having a tapered cutting edge, 52, intersecting one of its sides and intermittent, regularly spaced rectangular recesses, 54, formed in its cutting edge forming evenly sized teeth, 56, are disposed with their said sides facing one another, and a metal bar, 58, of a thickness to provide the desired space between the cutting edges, in the instance of the present invention such bar being one thirty-second of an inch thick, is placed between the blades, with the upper edge of the bar lying a distance below the cutting edges 52 of the blades 50; two shoulder blades, 60, having tapered upper edges, 62, likewise formed to intersect one of their sides, are disposed with their said sides set against the outer sides of blades 50 with the edges 62 terminating short of the edges 52 of the blades. The poured, solid-set, resilient mass, 64, fills the space between the cutting blades 50 above the spacing bar 58, the spaces between the teeth 56 formed in the cutting edge of'the blades, and the space above the edges of the shouder blades 60, to a level with the edges of the cutting blades 50. The rubber mass 64 will be all in one piece, the portions thereof above the shoulder blades and above the spacing plate being connected by the portions thereof lying in the spaces 54 between the teeth 56.

While the blades 50 have been shown with their cutting edges formed by a single taper on one side edge thereof and separated by a spacing bar, it may here be stated that their cutting edges may be formed by a double taper so as to be spaced from each of its sides; the angles of the tapers forming the cutting edges of such two knives being so arranged as to space such cutting edges the proper narrow distance as required.

The die knife section described above may be set in the wooden back of the cutting die in conventional manner, in appropriate position for forming the tear lines at the edges of the dust flaps 22 and 24, with one of its blades in alignment with the fold line defining the flapsu-pporting end wall panel from the lateraly adjacent blank portions, and the other blade outwardly disposed relative to the first.

To distort, loosen up and weaken the cardboard portions between the blades opposite the staggered cuts, so as to assure a zigzag, teeth-forming tear and to provide a flexible connection of' the base of the teeth with the flap proper, spaced, built-up mats, 66 and 68, may be provided on the steel jacket, 70, on which the blank is cut and scored. One of the mats, as 66, may be thicker than the other, as by being formed of two plies of material, such as cardboard, as compared to a single ply for the second mat 68, and such thicker mat 66 may be disposed With its longitudinal edge in vertical alignment with inner of the knife blades 50. The other of the mats may be spaced outwardly of the first mat, a distance preferably wider than the thickness of the knife. Thus, when the die is lowered on the blank interposed between it and the jacket 70, the two blades 50 will form the two rows of intermittent cuts and, at the same time, the resilient mass 64 will press down on the cardboard material underlying the knife to stretch the material between mats 66 and 68 and also form a fold line, 72, which is sharply defined, adjacent the edge of the thicker mat 66 which coincides substantially with the inner row of intermittent cuts (FIGS. 10 and 11). This distortion and softening of the cardboard material between the blades of the knife tends to dela'minate the cardboard fabric, at least to a certain extent, to stretch the fibers in the distorted portion of the blank, which lie with the grain of the cardboard, and to cause defibrillation, to an extent, of the edges of the teeth formed when the dust flap is severed from its laterally adjacent blank portions, rendering the row of teeth connected to the dust flap compressible and bend-able at their bases.

It may here be stated that suitable plows may be provided on the sealing apparatus, in appropriate position to sever the dust flaps from the adjacent blank portions, along the tear line, as the folded and setup blank is moved on the apparatus. It may here also be stated that the recesses between teeth 28 may be of greater depth than width.

While the illustrated blank represents a preferred embodiment of the invention, for the production of a carton that will be siftproof for even the most highly pulverized substances, of the highest mesh, it may here be stated and be understood that for cartons for holding pulverized solids of lesser mesh, the teeth 28 need not extend the full length of the dust flap edges but may extend only along the inner portion thereof; the most critical tooth being the first tooth at the inner ends of the dust flap edges, which tooth must be directly disposed against fold lines 23 and 25 as the case may be. A so positioned tooth will be sufficient, in many instances, to close any possible pin holes at the corners of the car-ton that frequently occur in conventional cartons.

This completes the description of the carton blank of the present invention and the method by which it may be produced and the carton which may be formed with it, as well as the means by which such blank may be produced and the method of producing such means.

It will be apparent that the blank of the present invention may be readily formed at their regular rate of speed on conventional apparatus which need be modified by only minor additions. It will also be apparent that such blanks may be glued, folded and erected and sealed on conventional apparatus at the regular rate of speed of the apparatus, and that such apparatus, likewise, need not be materially modified, any modification consisting merely of adding a few simple parts thereto.

It will be further apparent that numerous variations and modifications may be made in the carton blank of the present invention by anyone skilled in the art, in accordance with the principles of the invention set forth above and without the exercise of any inventive ingenuity. I desire, therefore, the protection of the .patent laws for any and all such variations and modifications that may be made within the spirit of the invention and the scope of the claims appended hereto.

What-I claim is:

1. A blank for a cardboard carton, of the character described, including pairs of opposed wall panels defined from one another by fold lines, one pair of said opposed Wall panels each having a dust fiap at one end defined therefrom by a fold line and another pair of said opposed wall panels each having a closure flap at the corresponding end defined therefrom by a fold line; said closure flaps adapted to be disposed over said dust flaps when said blank is set up and sealed; said blank having a small projection protruding into the corner formed 'by at least one side edge of each said dust flap with the edge of the wall panel supporting the adjacent closure flap, said projection connected to said dust flap and formed from part of said adjacent closure flap, one edge of said projection defined by the edge of said wall panel supporting said adjacent closure flap.

2. The carton blank of claim 1, wherein the fold line defining each said dust flap from its supporting wall panel is bent and has an apex extending in the direction of said dust flap.

3. The carton blank of claim 2, wherein a partly cut fold line is formed in each said dust flap extending longitudinally at the center thereof from said peaked fold line to its outer edge, said cut in said fold line formed in the outer surface of said dust flap.

4. The blank of claim 1, wherein said projection has its fibrous structure weakened to render it yieldable relative to the adjacent blank areas.

5. A cardboard blank for a carton, of the character described, including pairs of opposed wall panels defined from one another by fold lines oriented for folding into tubular form, one pair of said panels each having a dust flap connected thereto at one end and defined therefrom by a fold line, and another pair of said panels each having a closure flap at said end defined therefrom by a fold line, said closure flaps adapted to be disposed over said dust flaps when said blank is set up and sealed, said dust flaps being of excessive width relative to the width of the wall panel to which it is connected and overhanging the adjacent wall panel on at least one side of said connected wall panel at a point immediately adjacent thereto, said excess width portion being narrow and having a weakened fibrous structure rendering it yieldable relative to the remainder of the structure of the dust flap.

6. The carton blank of claim 5, wherein said excess width extends substantially the height of said side edge of said dust flap.

7. The carton blank of claim "5, wherein said portion of said dust flap forming said excess width has spaced recesses formed therein opening into its said side edge.

8. The carton blank of claim 7, wherein said recesses are closely and evenly spaced from one another and of a size substantially equal to one another and to the space separating them from one another.

9. The carton 'blank of claim 5, wherein said dust flaps are each provided with at least one longitudinally extending fold line oriented to fold in the same direction as said panel defining fold lines.

10. A blank for a cardboard carton, of the character described, including pairs of opposed wall panels defined from one another by fold lines oriented to fold said panels into a tube, one pair of said wall panels each having a dust flap at one end defined therefrom by a fold line and another pair of said wall panels each having a closure flap at one end defined therefrom by a fold line, each said dust flap being of a length not greater than half of the width of an adjacent wall panel said closure flaps adapted to overlie said dust flaps when said blank is set up and sealed, each said dust flap having at least one longitudinally extending fold line formed therein at a midpoint thereof oriented for folding in the same direction as said panel defining fold lines whereby said dust flaps will fold outwardly against an overlying closure flap when said blank is set up and sealed.

11. A blank for a carton of the character described comprising a sheet of cardboard cut and scored to define two pairs of alternating panels defined from one another by parallel scored fold lines, the panels of one of said pairs each having a dust flap extension at an end thereof defined therefrom by a scored fold line, the wall panels of the other of said pair having a closure flap extension at said ends defined therefrom by a scored fold line, said dust flaps defined along their longitudinal edges from the laterally adjacent blank sections by a closely spaced pair of longitudinal rows of closely spaced cuts, one of said rows having its cuts substantially aligned with the scored fold line defining its supporting wall panel from the laterally adjacent blank section, the other of said rows of cuts disposed outwardly thereof, the first cut in said first row being spaced from the fold line defining said dust flap from its supporting wall panel.

12. The carton blank of claim 11, wherein said cuts in said rows are arranged in staggered relation to one another.

13. The carton blank of claim 11 wherein said rows of spaced cuts are spaced apart from one another a distance of approximately one thirty-second of an inch (%2")- 14. The carton blank of claim 13, wherein said cuts and the spaces between them are each approximately one thirty-second of an inch 15. The carton blank of claim 11, wherein a scored fold line is formed in the underside of said blank in the space between said row of cuts.

16. The carton blank of claim 15, wherein said fold line is deeper adjacent said first named row of cuts.

References Cited UNITED STATES PATENTS 88,165 3/ 1869 Hendryx. 2,329,628 9/1943 Lanigan 22937 3,182,887 5/ 1965 Larson 229-37 3,199,762 8/1965 Coons 229-41 DAVID M. BOCKENEK, Primary Examiner. 

